The present invention relates to intraocular lenses (IOLs) and a method for making and using the same. More particularly, the present invention relates to IOLs designed primarily for refractive correction in phakic eyes where the eye""s natural lens remains intact. IOLs made in accordance with the present invention may also be used in aphakic eyes where a diseased natural lens is surgically removed, such as in the case of cataracts.
Visual acuity deficiencies such as myopia (nearsightedness), hyperopia (farsightedness) and presbyopia (age-related farsightedness) are typically corrected with use of refractive lenses such as spectacles or contact lenses. Although these types of lenses are effective in correcting a wearer""s eyesight, many wearers consider the lenses inconvenient. The lenses must be located, worn at certain times, removed periodically and may be lost or misplaced. The lenses may also be dangerous or cumbersome if the wearer participates in athletic activities or suffers an impact in an area near the eyes.
The use of surgically implanted IOLs as a permanent form of refractive correction in phakic eyes has been gaining in popularity. IOL implants have been used for many years in aphakic eyes as replacements for diseased natural crystalline lenses that have been surgically removed from the eyes. Many different IOL designs have been developed over past years and proven successful for use in aphakic eyes. Successful IOL designs to date primarily include an optic portion with supports therefor, called haptics, connected to and surrounding at least part of the optic portion. The haptic portions of an IOL are designed to support the optic portion of the IOL in the lens capsule, anterior chamber or posterior chamber of an eye.
Commercially successful IOLs have been made from a variety of biocompatible materials, ranging from more rigid materials such as polymethylmethacrylate (PMMA) to softer, more flexible materials capable of being folded or compressed such as silicones, certain acrylics, and hydrogels. Haptic portions of the IOLs have been formed separately from the optic portion and later connected thereto through processes such as heat, physical staking and/or chemical bonding. Haptics have also been formed as an integral part of the optic portion in what is commonly referred to as xe2x80x9csingle-piecexe2x80x9d IOLs.
Softer, more flexible IOLs have gained in popularity in more recent years due to their ability to be compressed, folded, rolled or otherwise deformed. Such softer IOLs may be deformed prior to insertion thereof through an incision in the cornea of an eye. Following insertion of the IOL in an eye, the IOL returns to its original pre-deformed shape due to the memory characteristics of the soft material. Softer, more flexible IOLs as just described may be implanted into an eye through an incision that is much smaller, i.e., 2.8 to 3.2 mm, than that necessary for more rigid IOLs, i.e., 4.8 to 6.0 mm. A larger incision is necessary for more rigid IOLs because the lens must be inserted through an incision in the cornea slightly larger than the diameter of the inflexible IOL optic portion. Accordingly, more rigid IOLs have become less popular in the market since larger incisions have been found to be associated with an increased incidence of postoperative complications, such as induced astigmatism.
After IOL implantation, both softer and more rigid IOLs are subject to compressive forces exerted on the outer edges thereof, which typically occur when an individual squints or rubs the eye. These compressive forces may result in decentration of the IOL and distortion of the visual image. Compressive forces exerted on an IOL also tend to cause axial displacement of the IOL along the optical axis of an eye. Movement of an IOL along the optical axis of an eye has the potential in anterior chamber applications to cause the IOL to contact and damage the delicate corneal endothelial cell layer of the eye. Such potential damage to the delicate corneal endothelial cell layer is due in part to the design of anterior chamber IOLs that are vaulted to prevent interference or damage to the iris of an eye. Also, IOLs of current designs, whether vaulted or unvaulted, or formed of either softer or more rigid materials, tend to deflect along the optical axis of an eye when the haptics are compressed. IOL manufacturers provide a wide range of IOL sizes to more precisely fit IOLs to each particular patient""s eye size. Providing a wide range of IOL sizes is an attempt to minimize the potential for axial displacement of the IOL along the optical axis of an eye.
Because of the noted shortcomings of current IOL designs, there is a need for IOLs designed to minimize axial displacement of the IOL optic portion along the optical axis of the eye when compressive forces are exerted against the outer edges thereof. By lessening an IOLs movement along the optical axis of an eye, more certain refractive correction may be achieved and the risk of corneal endothelial cell layer damage may be reduced.
An intraocular lens (IOL) made in accordance with the present invention has an optic portion with an outer peripheral edge and two, three or four looped haptic elements for supporting the optic portion in a patient""s eye. A lens having two looped haptic elements is balanced by having a looped haptic element formed or attached on two opposed edges of the optic portion. A lens having three looped haptic elements is balanced by having a set of two looped haptic elements formed or attached on one edge of the optic and the third looped haptic element formed or attached on an opposite edge of the optic. A lens having four looped haptic elements is balanced by having a set of two looped haptic elements formed or attached on one edge of the optic and a set of two looped haptic elements formed or attached on an opposite edge of the optic. Each looped haptic element has an inner edge portion, an outer edge portion and generally two attachment portions that permanently connect the looped haptic elements to the outer peripheral edge of the optic portion. In the case of lenses having three or four looped haptic elements, a set of two looped haptic elements may have three attachment portions rather than four. In such a case, one of the three attachment portions is common to each of the two looped haptic elements in the set. Each looped haptic element also includes a flexible central portion located adjacent to each of the two attachment portions and a contact plate located between the two flexible central portions. The contact plate is designed to engage an inner surface of a patient""s eye. The two flexible central portions that extend between the contact plate and the attachment portions allow the lens to adjust to pressures exerted on the lens within the eye. Additionally, within these flexible central portions, each looped haptic element is designed to have greater resistance to bending in a plane generally parallel to the optical axis of an eye than in a plane generally perpendicular to the optical axis of an eye. By providing looped haptic elements with this type of flexibility characteristic, the present IOL fits eyes of varying sizes. The flexibility characteristic of the subject looped haptic elements relative to the optic portion also eliminates unacceptable axial displacement of the optic portion along the optical axis when compressive forces are exerted against the looped haptic elements of the IOL.
Accordingly, it is an object of the present invention to provide intraocular lenses for use in phakic eyes.
Another object of the present invention is to provide intraocular lenses for use in phakic eyes, which fit a variety of eye sizes.
Another object of the present invention is to provide intraocular lenses for use in phakic eyes, which minimize axial displacement of the optic portions of the lenses along the optical axis of the eyes.
Another object of the present invention is to provide intraocular lenses for use in phakic eyes, which minimize damage to tissues in the interior of the eyes.
Still another object of the present invention is to provide intraocular lenses, which are resistant to decentration within the eyes.
These and other objectives and advantages of the present invention, some of which are specifically described and others that are not, will become apparent from the detailed description, drawings and claims that follow, wherein like features are designated by like numerals.